JPH10271593A - Speaker equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a proper directivity to extend a listening position at which a preferable stereophonic sense is obtained. SOLUTION: A speaker SP1 is fitted to a front panel 11F of a box 11, and a speaker SP2 with the same diameter as that of the speaker SP1 is mounted on an upper panel 11U. The speaker SP1 is driven at a positive polarity of a signal, while the speaker SP2 is driven at a negative polarity of a signal. Drive voltages E1, -E2 of the speakers SP1, SP2 are selected according to a relation of E2/E1<1. That is, the radiation sound pressure of the speaker SP2 is decreased more than the radiation sound pressure of the speaker SP1. A directivity coefficient of the combined sound pressure of the speakers SP1, SP2 at a sound receiving position in a direction of 90 deg. is a product between a directivity coefficient D(90 deg.) of the speaker itself and a value (1-α) smaller than the unity and the output sound pressure of the speakers is reduced independently of the frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a speaker device provided with directivity. More specifically, a first speaker driven in a positive polarity is attached to a front panel of a speaker box, a second speaker driven in a negative polarity is attached to, for example, an upper panel of the speaker box, and radiation of the second speaker is further performed. The present invention relates to a loudspeaker device in which the sound pressure is made lower than the radiated sound pressure of the first speaker, thereby realizing a suitable directivity for expanding a listening position where a preferable stereo feeling is obtained.

[0002]

2. Description of the Related Art Conventionally, there are the following directional speakers.

[0003] For example, there is a tone zoire type directional speaker 20 as shown in FIG. The speaker 20 is configured such that a plurality of speakers (five speakers 22a to 22e in the figure) are linearly arranged in a line on a panel surface of a speaker box 21. This speaker 20 is shown in FIG.
By adopting a configuration in which a plurality of speakers are arranged in the horizontal direction as shown in FIG. 3, sharp directivity is obtained in a horizontal plane.

For example, there is a bidirectional speaker 30 as shown in FIG. This speaker 30 has two speakers 32a and 32b attached to the front and back of a baffle plate 31 facing each other, and driven with opposite polarities.

As will be described later, the loudspeaker device according to the present invention has a different structure and obtained directivity from the above-described conventional directional speaker.

[0006]

As shown in FIG. 15, a conventional two-channel stereo reproduction speaker 40 has a left speaker 41L and a right speaker 41R mounted on the front panel surfaces of speaker boxes 42L and 42R, respectively. The user listens with the front panel surface facing the front. In such a speaker 40, the listening position at which a preferable stereo feeling is obtained is limited to an extremely narrow range including the point a on the center line of both the left and right speakers as shown by oblique lines in FIG.

In this case, at point b deviated from the center line,
Since the distance from the listening position to the speaker is different on the left and right,
The sound of the left speaker 41L is small, and the sound of the right speaker 41R is loud. For this reason, at the point b, the sound image is localized in the direction of the right speaker 41R, and the original sound stage cannot be reproduced even as a two-channel stereo.

As a method of improving such a problem, that is, a method of reproducing two-channel stereo sound intended to expand a listening position where a preferable stereo feeling can be obtained, a method utilizing the directivity of a speaker has conventionally been adopted.

A two-channel stereo reproduction speaker 50 shown in FIG. 16 has closed cabinets 52L and 52R with reference axes of the left speaker 51L and the right speaker 51R directed inward by about 45 ° from the center listening position. Which uses a directivity that depends on the diameter of the speaker and the size and shape of the cabinet.

That is, the listening position deviated from the center line,
For example, at the point b, the listening position at which a preferable stereo feeling can be obtained by the function of correcting the level difference between the L and R signal sounds based on the difference in the distance from both speakers so as to be smaller by the directivity of the speakers. It is about to expand.

However, the directivity depending on the diameter of the speaker and the shape and size of the cabinet generally starts at a higher frequency as the diameter of the speaker is smaller, and becomes almost omnidirectional at the middle and low frequency bands. In particular, directivity at a frequency of 1 kHz or less greatly affects the effect of expanding the listening position. In FIG. 16, a curve w1 shows a directivity pattern at middle and high frequency bands, and a curve w2 shows a directivity pattern at middle and low frequency bands. Point a is a point on the center line of both the left and right speakers, as in FIG.

The directivity that can further expand the listening position is shown in FIG.
As shown by a curve w3 in FIG. 7, when the front direction of the reference axis of the speaker is set to 0 °, directivity is required such that the sound pressure gradually decreases from 0 ° to 90 °. It is desirable that the sound pressure is reduced by 6 dB or more in the ゜ direction.

Therefore, according to the present invention, for example, at a frequency of 1 kHz or less, the directivity capable of lowering the sound pressure by 6 dB or more in the 90 ° direction as compared with the 0 ° direction (front direction), and thus the listening position where a preferable stereo feeling is obtained is expanded. It is an object of the present invention to obtain suitable directivity.

[0014]

According to the speaker device of the present invention, a first speaker is attached to a front surface of a speaker box when the speaker box is installed, and the first speaker is attached to one of an upper surface, a lower surface, and a back surface of the speaker box when the speaker box is installed. A second speaker is attached, the first speaker is driven with a positive polarity, and the second speaker is driven with a negative polarity, so that the radiated sound pressure of the second speaker is smaller than the radiated sound pressure of the first speaker. Things.

In the 90 ° direction, the directivity coefficient of the combined sound pressure of the first and second speakers at the sound receiving position is smaller than 1 which is (1-α) which is the directivity coefficient D (90 °) of the speaker alone. Multiplied by the value. In other words, in the direction of 90 °,
The output sound pressure of the speaker can be reduced regardless of the frequency. In this case, the decrease rate of the output sound pressure gradually increases from 0 ° to 90 °, and reaches a maximum (1−1) at 90 °.
α), and changes so as to gradually decrease from 90 ° to 180 °.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a speaker device 10 as an embodiment.

A first speaker SP1 is mounted on a front panel (front panel) 11F with the rectangular parallelepiped speaker box 11 installed. Also, the speaker box 11
The first speaker SP is mounted on the upper panel 11U in the installation state.
A second speaker SP2 having the same diameter as the first speaker SP2 is attached. In this case, the speaker SP2 is attached so that its reference axis L2 extends in the direction of the reference axis L1 of the speaker SP1.

The speaker SP1 is driven with a positive polarity, and the speaker SP2 is driven with a negative polarity. The drive voltages E1 and -E2 of the speakers SP1 and SP2 are equal to E2
/ E1 <1 is an arbitrary value that satisfies <1. This allows
As described above, since the speakers SP1 and SP2 have the same diameter, the radiation sound pressure of the speaker SP2 is smaller than the radiation sound pressure of the speaker SP1.

FIG. 3 shows a drive circuit 13 for the speakers SP1 and SP2. Output audio signal SA of signal source 15
Are amplified by the amplifier 16 and supplied to the speaker SP1. Thus, the speaker SP1 is driven with the positive polarity by the drive voltage E1. The output audio signal SA of the signal source 15 is attenuated by the attenuator 17, amplified and inverted by the amplifier 18, and supplied to the speaker SP2. As a result, the speaker SP2 outputs the drive voltage −E2 (E2 <E
According to 1), it is driven with a negative polarity.

As another method for making the driving force of the speaker SP2 smaller than that of the speaker SP1, the speaker SP
There is a method of making the voice coil resistance value of the voice coil 2 larger than the voice coil resistance value of the speaker SP1. In this case, the voice coil current of speaker SP2 is smaller than the voice coil current of speaker SP1, and the driving force of speaker SP2 can be smaller than the driving force of speaker SP1. This method has an advantage that both speakers can be driven in parallel by one amplifier.

In the structure shown in FIG.
Assuming that the vibration speed of the diaphragm of the speaker SP1 when the speaker SP2 is driven at the same time by the driving force of 1 and the driving force of −F2 by the driving force of −F2 is represented by Expression (1).

[0022]

(Equation 1)

Here, V0 is expressed by equation (2), s0 is the equivalent stiffness of the diaphragm, m0 is the effective mass of the diaphragm, r0
Is the equivalent mechanical resistance including the electromagnetic braking resistance, and s1 is the equivalent stiffness exhibited by the air in the box. Ω0 is the lowest resonance angular frequency of the diaphragm itself generated by m0 and s0, and Q0 is the Q of the resonance.

[0024]

(Equation 2)

Next, assuming that the vibration speed of the speaker SP2 is V2, it is expressed by the following equation (3).

[0026]

(Equation 3)

Here, the second term in ｛｝ in the equations (1) and (3) is caused by mutual influence based on the fact that both speakers have a common air chamber. Can be handled as follows. That is, the second term in ｛｝
It has a second-order LPF (low-pass filter) characteristic, and its cutoff frequency f0 is the lowest resonance frequency of the speaker diaphragm. This f0 can be generally set to a low frequency of 200 Hz or less, and it is extremely easy to set s1 / s0≪1 depending on the setting of the inner volume of the box.

Therefore, if the frequency range of about 200 Hz or more is targeted, the second term in the square may be omitted compared to the first term.

Therefore, if the second term in ｛｝ is omitted, V
1 and V2 are expressed as in equations (4) and (5), respectively. V1 = V0 (4) V2 = -V0 (F2 / F1) (5)

Here, in order to theoretically study the synthetic sound pressure of the sound waves radiated from the speakers SP1 and SP2, a concept as shown in FIG. 4 is taken. Note that the spatial distance between the front surface of the speaker SP1 and the center of the opening surface of the speaker SP2 is d. Also, the speaker SP1 and the speaker S
Focusing on a one-way component of the sound wave radiated from P2 in the horizontal plane, the front direction of the reference axis L1 of the speaker SP1 is set to 0 °, and the angle between the direction of interest and the direction of interest is defined as θ in the clockwise direction.

In FIG. 4, when the distance r between the sound receiving position and the speaker is 1 m or more, the sound wave at the sound receiving position is
It can be regarded as almost a plane wave. In addition, since the diaphragm of the speaker has a finite area, the sound waves radiated from this surface have directivity depending on the diameter of the speaker as the frequency increases, in relation to the size and shape of the box. The larger the aperture, the more directivity begins at lower frequencies.

Therefore, the directivity coefficient of such directivity is represented by D
If expressed as (θ), the sound pressure P1 (θ) at the sound receiving position of the sound wave radiated from the speaker SP1 is expressed by equation (6). S is the effective area of the diaphragm, ρ is the density of air,
c is the speed of sound.

[0033]

(Equation 4)

Next, regarding the sound wave radiated from the speaker SP2, since the speaker SP2 is attached to the upper panel U of the speaker box 11, the directivity coefficient in the horizontal plane is in the range of θ = 0 ° to 360 °. And always D (9
0 °). The sound pressure P2 (θ) at the sound receiving position is
A time delay of dcos θ occurs with respect to P1 (θ), and the speaker SP2 is driven by a negative voltage −E2 different from the speaker SP1. Therefore, the sound pressure P2 at the sound receiving position of the sound wave radiated from the speaker SP2
(Θ) is represented by equation (7), where the vibration speed of the diaphragm is −V2.

[0035]

(Equation 5)

Therefore, the synthetic sound pressure P (θ) is P1
Since it is (θ) + P2 (θ), it is expressed by equation (8).

[0037]

(Equation 6)

Therefore, if F2 / F1 = α <1, then:
Equation (8) is represented as equation (9).

[0039]

(Equation 7)

The sound pressure P0 at the sound receiving position of the sound wave in the front direction (θ = 0 °) radiated from the speaker SP1 is:
It is expressed by equation (10). Therefore, P (θ) / P0 is
It is expressed by equation (11).

[0041]

(Equation 8)

Equation (11) represents the directivity coefficient of the synthesized sound pressure at the sound receiving position. In the equation (11), ω / с = k
When expressed by a trigonometric function, equation (11) is represented as equation (12).

[0043]

(Equation 9)

Therefore, θ = 0 °, 90 °, 180 °
When the directivity coefficient of the direction is obtained from Expression (12), (13)
Expressions (14) and (15) are used.

[0045]

(Equation 10)

Here, the directivity depending on the speaker diameter and the shape and size of the box is omni-directional at low frequencies.
Therefore, the directivity coefficient at low frequencies is D (0 ゜) ≒ D (9
0 ゜) ≒ D (180 ゜) ≒ 1. At a low frequency of kd≪1, coskd ≒ 1 and sinkd ≒ kd, and kd can be omitted compared to 1. Therefore, the expressions (13), (14), and (15) all take a value of 1-α. That is, at a low frequency, the directivity of the synthesized sound pressure becomes the omnidirectional value of 1-α.

Next, as the frequency increases, directivity depending on the aperture of the speaker and the shape and size of the box starts to be imparted, and the higher the frequency, the sharper the directivity. However, FIG.
The characteristic of the directivity of the speaker device 10 shown in (1) is that the directivity coefficient in the 90 ° direction becomes (1-α) as the directivity coefficient D (90 °) of the speaker as shown in Expression (14). Since the value is multiplied by a smaller value, the output sound pressure of the speaker can be further reduced in the direction of 90 ° regardless of the frequency. This decrease in output sound pressure is 90
゜ Not only in one direction. In this case, the decrease rate of the output sound pressure gradually increases from 0 ° to 90 °, reaches a maximum (1−α) at 90 °, and gradually decreases from 90 ° to 180 °. 10
The output sound pressure characteristic and the directivity of will be described more specifically based on the measurement results.

In this case, the dimensions of the speaker box 11 are such that the mounting surface of the speaker SP1 is vertical and horizontal, 11 cm square, and 16 cm deep. Speaker SP1, S
As P2, dynamic speakers each having a diameter of 8 cm are used. d is set to 10 cm.

Next, the measurement results will be described.

FIG. 5 shows the output sound pressure directional frequency characteristics when only the speaker SP1 is driven by 0 °, 90 °, 180 °.
This is the result of measuring θ in three directions in an anechoic chamber. According to FIG. 5, the directivity at a frequency of about 300 Hz or less is almost omni-directional. The output sound pressure characteristics in the 90 ° and 180 ° directions at a frequency of 300 Hz or more show, on average, almost −6 dB / oc as the frequency increases.
It decreases at the rate of t. This indicates that the directivity at a frequency of 300 Hz or more becomes sharper as the frequency increases.

Therefore, when the directivity pattern when only the speaker SP1 is driven is actually measured, FIG. 6 and FIG.
It becomes as shown in. The measurement frequency is 200Hz, 500
Hz, 1 kHz, 2 kHz, 5 kHz, 10 kHz
Frequency. As is clear from FIGS. 6 and 7, the directivity becomes sharper as the frequency increases.

However, when only the speaker SP1 is driven, at a frequency lower than 500 Hz, the directivity is almost nearly omni-directional, and the sound pressure in the 90 ° direction is higher than the sound pressure in the front direction (θ = 0 °). Pressure drop is too small. Therefore,
It is not preferable as the directivity which has the effect of expanding the listening position where a preferable stereo feeling can be obtained.

Next, both the speakers SP1 and SP2 are
An actual measurement result when driven according to the above theory will be described.

First, FIG. 8, FIG. 9 and FIG.
Are set to 0.316 (−10 dB) and 0.5 (−6 dB).
4B shows the results of actual measurements of the output sound pressure directivity frequency characteristics in three directions of 0 °, 90 °, and 180 ° when B) and 0.708 (−3 dB). According to this, at low frequencies, that is, in this case, at a frequency of about 200 Hz or less, almost no directivity is provided as described in the theoretical study, but at frequencies higher than 300 Hz, 9
The sound pressure characteristic in the 0 ° direction is, on average, the speaker SP.
Compared to the case where only 1 is driven, about -3 dB at α = 0.316, about -6 dB at α = 0.5, and α = 0.70
In FIG. 8, it is reduced by about -10 dB.

The sound pressure characteristic in the 180 ° direction has a peak and a dip, and tends to increase on average as compared with the case where only the speaker SP1 is driven. However, 1
The sound wave in the 80 ° direction is a sound wave radiated behind the speaker when viewed from a general listening condition, and therefore does not directly affect the effect of expanding the listening position.

Next, the sound pressure characteristic in the front direction, that is, in the 0 ° direction, is such that the lower limit of the reproduction band is slightly narrowed as compared with the case where only the speaker SP1 is driven, and the change in the frequency characteristic is small. is there.

At a frequency of 200 Hz or less,
The sound pressure in the 0 ° direction tends to be slightly higher than the sound pressure in the 90 ° direction, and conversely, the sound pressure in the 180 ° direction tends to be slightly lower. This tendency increases as the value of α approaches 1.

This phenomenon is a problem depending on the distance between the speaker and the sound receiving position, and is based on the following reason.

That is, in the above theoretical study, the directivity at a low frequency is reduced to the omni-directional property under the condition that the spatial distance d between the two speakers is sufficiently negligible compared to the distance r between the speaker SP1 and the sound receiving position. Said to be. However, in the actual measurement data shown in the text, d is 10 cm, while γ is 100 cm. Therefore, in the 0 ° direction, the distance between the speaker SP2 and the sound receiving position is 110 cm, and in the 180 ° direction, the distance is 90 cm.

For this reason, the distance between the speakers SP1 and SP2 and the sound receiving position is 100 cm and 110c in the 0 ° direction.
m, 180 ° direction, 100cm and 90cm, 1
A difference between both sound pressures due to a difference of 0 cm, that is, a difference of 10%, causes the above phenomenon. Just 10
%, This phenomenon occurs because the combined sound pressure at the sound receiving position is not a vector sum of the sound waves radiated from the speakers SP1 and SP2, but a vector difference, and is therefore a bidirectional pattern. Alternatively, this is exactly the same phenomenon as the proximity effect unique to a unidirectional microphone. Such a proximity effect increases as the sound receiving position is closer to the sound source.

The above are the output sound pressure frequency characteristics in three directions of 0 °, 90 °, and 180 °. Next, the results of actual measurement of directivity patterns at several frequencies will be described.

FIGS. 11 and 12 are directional patterns corresponding to the directional patterns when only the speaker SP1 shown in FIGS. 6 and 7 is driven. The value of α is 0.
5

When comparing the directivity pattern at a frequency of 2 kHz or more with FIG. 7 and FIG. 12, the directivity coefficient in the 90 ° direction is lower in FIG. The pattern does not change much.

However, at frequencies above 2 kHz, SP
Since only 1 has a sharp directivity, the speaker SP1 alone is sufficient as the directivity having the effect of expanding the listening position to obtain a preferable stereo feeling.

On the other hand, comparing FIG. 6 with FIG. 11 for the directivity pattern of 1 kHz or less, the directivity coefficient in the 90 ° direction is reduced to 、 in FIG. Sex pattern has been obtained. Therefore, according to the speaker device 10 shown in FIG. 1, it is possible to obtain directivity suitable for expanding a listening range in which a preferable stereo feeling is obtained.

In the above-described embodiment, the speaker SP2 is mounted on the upper panel 11U with the speaker box 11 installed. However, the speaker SP2 may be mounted on the lower panel or the rear panel. . In the above embodiment, the speakers SP1 and SP2 have the same diameter, but the speakers SP1 and SP2 may have different diameters. Even in such a case, it is necessary to make the radiation sound pressure of the speaker SP2 smaller than the radiation sound pressure of the speaker SP1.

[0067]

According to the speaker device of the present invention,
A first speaker driven in a positive polarity is attached to a front panel of the speaker box, a second speaker driven in a negative polarity is attached to, for example, a top panel of the speaker box, and a radiated sound pressure of the second speaker is reduced to a second level. The directivity coefficient of the combined sound pressure of the first and second speakers at the sound receiving position is smaller than the directivity coefficient of the single speaker in the 90 ° direction. Multiplied by the value. Therefore, for example, 1k
90 Hz compared to 0 ° direction (front direction)
It is possible to obtain a directivity capable of lowering the sound pressure by 6 dB or more in the ゜ direction, and thus a suitable directivity for expanding a listening position where a preferable stereo feeling is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a speaker device according to an embodiment.

FIG. 2 is a view schematically showing a cross section of the speaker device.

FIG. 3 is a diagram showing a driving circuit of speakers SP1 and SP2.

FIG. 4 is a diagram for theoretically analyzing a combined sound pressure of radiated sound waves of speakers SP1 and SP2.

FIG. 5 is a diagram showing output sound pressure directivity frequency characteristics when only a speaker SP1 is driven.

FIG. 6 is a diagram showing a directivity pattern (200 Hz, 500 Hz, 1 kHz) when only the speaker SP1 is driven.

FIG. 7 is a diagram showing directivity patterns (2 kHz, 5 kHz, and 10 kHz) when only the speaker SP1 is driven.

FIG. 8 is a diagram illustrating output sound pressure directivity frequency characteristics (α = 0.316) when both of the speakers SP1 and SP2 are driven.

FIG. 9 is a diagram illustrating output sound pressure directivity frequency characteristics (α = 0.5) when both of the speakers SP1 and SP2 are driven.

FIG. 10 is a diagram showing output sound pressure directivity frequency characteristics (α = 0.708) when both of the speakers SP1 and SP2 are driven.

FIG. 11 shows directivity patterns (200 Hz, 500 Hz, 1 kHz) when both speakers SP1 and SP2 are driven.
It is a figure showing z).

FIG. 12 shows directivity patterns (2 kHz, 5 kHz, 10 kHz) when both speakers SP1 and SP2 are driven.
It is a figure showing z).

FIG. 13 is a diagram showing a conventional directional speaker (tone zoire type directional speaker).

FIG. 14 shows a conventional directional speaker (bidirectional speaker).
FIG.

FIG. 15 is a diagram illustrating an example of a speaker for two-channel stereo reproduction.

FIG. 16 is a diagram showing another example of a two-channel stereo reproduction speaker.

FIG. 17 is a diagram showing directivity that can enlarge a listening position where a preferable stereo feeling is obtained.

[Explanation of symbols]

 Reference Signs List 10 speaker device 11 speaker box 11F front panel 11U top panel 12 partition plate 13 drive circuit SP1 first speaker SP2 second speaker

Claims (2)

[Claims] A first speaker attached to a front panel in a state where the speaker box is installed, and a second speaker attached to one of an upper surface, a lower surface, and a rear surface in a state where the speaker box is installed; The second speaker is driven with a negative polarity, and the radiated sound pressure of the second speaker is made smaller than the radiated sound pressure of the first speaker. apparatus. 2. The speaker according to claim 1, wherein the first and second speakers have the same diameter, and the driving voltage of the second speaker is smaller than the driving voltage of the first speaker. apparatus.